1) A plasma specimen with a high titer of HIV RNA was identified and tested for use as the first generation CBER standard. A second standard based on culture supernatant from infected cells (clade B) was developed. Both materials have been evaluated in international collaborative studies involving the NIBSC and WHO for assessment of assay performance. The plasma specimen in a lyophilized form has been accepted as the first in international WHO standard. Currently, the laboratory is focussing on developing an HIV-1 subtype panel. Two isolates from each clade have been cultured to high titers. In a limited collaborative study, the copy numbers were estimated in the samples by the TMA, PCR and bDNA techniques. These reagents will be useful in regulatory and global assay standardization efforts. 2) In-house serologic and genetic assays and Taqman probes are being developed for HIV-1 group O and non clade B subtypes. An in-house HIV group O ELISA and primers and probes for HIV group O and M have been developed. The probes will be used to generate microarray based assays for viral genotype. These assays will serve as tools in molecular epidemiologic studies to determine prevalence of non clade B strains particularly HIV-1 group O in endemic areas. We have recently initiated a study to study molecular evolution of HIV in Camerooon a region which harbors several subtypes. We are also comparing the performance of various direct viral marker assays such as PERT, RT- PCR, and p24 assays for their ability to detect viral variants and HIV in the early phase of infection.